This invention relates to an apparatus for vibrating the ulna in vivo, and more specifically, to an apparatus for externally vibrating the ulna in vivo which is useful for measuring the resonant frequency of the ulna in vivo by imparting vibratory motion to it externally and examining the dynamical properties of the bone from the resonant frequency measured.
About 1970 Jurist and other workers pioneered a method for measuring the resonant frequency of the ulna or tibia in vivo by externally applying to it a vibratory motion having a frequency of 100 to 1,000 Hz and examining the dynamic properties of the bones from the resonant frequency measured. They point out that the product FL of the resonant frequency F of the ulna and the ulnar length L in patients with osteoporosis, diabetes, etc. evidently differs from FL in normal healthy persons [J. M. Jurist, "Phy, Med. Biol.," 15, 417 (1970); J. M. Jurist, "Phy. Med. Biol.," 15, 427 (1970); and K. F. Konkel & J. M. Jurist, "Wis. Med. J.," 72, 123 (1973)]. Some apparatuses for measuring such resonant frequencies F have also been proposed [see, for example, U.S. Pat. No. 3,477,422 to J. M. Jurist, and Japanese Laid-Open Patent Publication No. 111,484/1974].
It is, however, difficult to measure the inherent resonant frequency of a bone in vivo while minimizing interferences by other bones, muscles, etc., and according to the apparatuses proposed heretofore, it is difficult to measure resonant frequencies accurately with good reproducibility.
The present inventors made extensive investigations about a method for measuring the resonant frequency of a living bone of a forearm, especially the ulna, and found that the resonant frequency of the ulna considerably varies with the direction of the hand and this is because the supination and pronation of the forearm exert different effects on the force acting on the bone through the ligament. These investigations have finally led to the discovery that the reasonant frequency of the ulna can be measured accurately if vibratory motion is imparted to the elbow in such a way as to minimize any external force on the bone and to allow the ulna to vibrate freely in the transverse direction while its both ends are kept free.